Slide valves of this type are known, and are used, for example, in the chemicals or food industry for blocking lines for a wide variety of media where the latter can be liquid or gaseous materials and also solids, for example fuels, chemical liquids, granules, cereals etc. The slide valves are respectively provided with a housing having a passage opening and with a slider plate moveable within the housing at right angles to the passage opening and which can be displaced from an open position into a closed position blocking the passage opening tightly by means of a drive mechanism. A lateral seal is respectively disposed in a respective groove in the housing above the passage opening on both sides of the slider plate at right angles to its direction of displacement. The slide valves must meet high criteria with regard to fire safety, in particular when being used in areas where there is a risk of fire—both internally and externally.